<!DOCTYPE html>
<html lang="en">

<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
    <style>
        .Site {
            display: flex;
            min-height: 100vh;
            flex-direction: column;
            background-color: pink;
        }

        .Site-content {
            flex: 1;
            background-color: skyblue;
            margin: 10px 0;
        }

        header,
        footer {
            background-color: #ccc;
        }
    </style>
</head>

<body class="Site">
    <p>有时，页面内容太少，无法占满一屏的高度，底栏就会抬高到页面的中间。这时可以采用Flex布局，让底栏总是出现在页面的底部。</p>
    <header>...header</header>
    <main class="Site-content">...content</main>
    <header>...header</header>

</body>

</html>